Along with the Internet, I consider the Global Positioning Satellite system the greatest Defense Department invention of the past three decades. Among other things, it answers (with great accuracy) that old '60s question, "Where you at, man?"

Developed by Defense to provide pinpoint navigation accuracy for ships, planes and ground troops, as well as acting as the satellite brains behind precision weapons, GPS also is the core technology behind the Federal Aviation Administration's next-generation air traffic control system. It's also revolutionized mapping and surveying since the first GPS satellite was launched in 1978.

But Defense will not be able to target its missiles (and parents will not be able to track down missing Heathers, Jonahs or Fidos) if GPS is jammed or knocked out -- a problem the Transportation Department examined in great detail in 2001 in what was called the Volpe report.

That report recommended a backup for GPS to insure uninterrupted access to precise positioning, navigation and timing signals. Since then, the bureaucracies at the departments of Defense, Transportation and Homeland Security (specifically the Coast Guard) have been, what else, studying and analyzing the problem.

It now looks like the winner of the GPS backup sweepstakes is …

Back to the Future with eLORAN

In World War II, the United States developed and fielded an electronic navigation system called LORAN (short for Long Range Navigation) which, for the day, provided relatively precise position information (from one quarter of a nautical mile to one nautical mile versus often less than 30 feet or better for GPS). LORAN calculated positioning by computing the time difference between signals transmitted by a master and at least two LORAN slave stations.

Before the Volpe report came out, the Coast Guard considered shutting down LORAN stations because GPS provided a more accurate signal and did not eat up funding for operations and maintenance.

But the potential of GPS outages suddenly made LORAN, which transmits low-frequency signals at high power, look like a good backup to GPS, whose high-frequency, low-power signals are much more susceptible to jamming than LORAN.

Enhanced LORAN (or eLORAN) stations broadcast a data channel to beef up accuracy and signal availability and integrity. The International LORAN Association says this boosts position accuracy to between eight and 65 feet, with availability measured at 0.999 and integrity at 0.9999.

That's good enough to make eLORAN the preferred backup to GPS for aviation use, including en-route navigation, terminal and nonprecision approaches, according to a report released this month by the multiagency Joint Planning and Development Office, charged with developing by 2025 the Next Generation Air Transportation System in the United States. (JPDO members include the White House Office of Science and Technology, FAA, NASA and the departments of Commerce, Defense, Homeland Security and Transportation.)

eLORAN received the highest overall rating as a GPS backup in the report prepared for a wide range of aviation stakeholders, including airlines, general aviation users and government and standards organizations. The report, prepared by ITT, which last month won the FAA next-generation air traffic control contract, noted that due to limited international and oceanic coverage for aviation use, eLORAN should be backed up by aircraft inertial navigation systems in those areas.

Zachariah Conover, president and chief executive officer of CrossRate Technology, which has developed an integrated GPS/LORAN receiver, views the JPDO report as a strong endorsement of eLORAN as the best backup, saying that "no one can now argue with its technical merits as a backup to GPS."

The key question now, Conover said, is funding the continued deployment and operation of eLORAN stations in the United States.

Can Anyone Spare $450 Million?

Coast Guard Capt. Curtis Dubay provided a strong endorsement of eLORAN in a presentation to the National Position Navigation and Timing Advisory Board this month. The presentation mirrored the JPDO report to meet the strict criteria needed as a backup to GPS for aviation users.

The Coast Guard operates 24 LORAN stations, with 19 modernized to handle the eLORAN data channel, DuBay said. In order to provide full U.S. eLORAN coverage, he said the Coast Guard will upgrade the remaining five stations, build three new ones and add monitoring stations to check integrity and accuracy, plus operate and maintain the system.

He estimated this would cost $400 million for modernization and another $50 million for coverage expansion. Conover said which agency will foot this bill is the sticking point in designating eLORAN as the GPS backup.

Conover, who worked on LORAN during his tour in the Coast Guard, views Dubay's cost estimates as too high. But even if the total eLORAN bill did come in at $450 million, he views it as a small price for a backup to the multibillion-dollar GPS system, which has become embedded in the global economy.

Dubay said a multiagency team will study and assess (of course) all the reports and studies on eLORAN as a GPS backup. Conover said he expected a green light for eLORAN by the end of this year.

250 Million Dead Cell Phones?

One key example of how GPS has become integral to modern life that is far from its original purpose is its use by the mobile or cellular telephone industry for precision network timing.

Mitchell Narrins, senior systems engineer with the FAA's Navigation and Landing Product team,told an international GPS forum in Geneva in May that an estimated 100 million mobile phones in the United States, and another 250 million globally, rely on GPS for precision timing.

He then noted that Sprint Nextel told Transportation this year in a request for public comments on whether or not to forge ahead with an eLORAN system that "under no circumstances should the government place total reliance on GPS and completely abandon its plans to deploy eLORAN."

I sure don't want my cell phone to die because of a lack of a precision timing signal, but I would not mind selective outages for people who feel compelled to bellow on their phones after they get on a commercial flight. "Hi, honey, I'm on the plane."

The Digital Fuller Brush Man

That's how Kevin Carroll, who retired this month as Army program executive officer for enterprise information systems, described his new role as a consultant to the federal information technology industry.

Carroll said he has a sample bag filled with ones and zeroes and is going door to door to find about five clients who want to sign up with his boutique consulting shop.

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